Control for refrigerating apparatus



May 22, 1951 Original Filed Aug. 1, 1941 A. B. NEWTON CONTROL FORREFRIGERATING APPARATUS 3 SheetsSheet 1 May 22, 1951 A. B. NEWTON2,553,979

CONTROL FOR REFRIGERATING APPARATUS Original Filed Aug. 1, 1941 r 3Sheets-Sheet 2 w m /Z5 4 l1 Fig.5 o

if f Fzfui Ennentor fll. wnv J9. NEWTON Gtforneg y 22, 1951 A. B. NEWTON2,553,979

CONTROL FOR REFRIGERATING APPARATUS Original Filed Aug. 1, 1941 5Sheets-Sheet 3 wu'l:

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Snventor HAW/N E NEWTON (Ittorneg Patented May 22, 1951 CONTROL FORREFRIGERATIN G APPARATUS Alwin B. Newton, Minneapolis, Minn., assignorto Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., acorporation of Delaware Original application August 1, 1941, Serial No.405,032. Divided and this application April 13, 1944, Serial No. 530,816

13 Claims. Cl. 175-320) This is a divisional application of myco-pending application, Serial No. 405,032, filed August 1, 1941, nowPatent No. 2,367,306, issued January 16, 1945.

The invention herein disclosed relates primarily to controls forrefrigerating systems, particularly, systems having a compressor,condenser and an evaporator connected in operative circuit relationship.

One of the main objects of the invention is to provide an improvedarrangement for controlling the compressor wherein the compressor isnormally started in response to suction pressure but wherein there aremeans for starting the compressor in response to ambient temperature,the latter means being arranged to be affected by heat generated as anincident to operation of the system for retracting it from compressorstarting position.

Another object is to make the temperature responsive means in the formof a timer so as to remain out of starting position of the compressorfor a predetermined time to prevent it from causing short cycling of thecompressor.

The ambient temperature responsive means of the foregoing objects isparticularly advantageous and desirable where the compressor is locatedin a relatively cold location such that the suction pressure might notrise high enough to cause the compressor to start. The heat applied tothe ambient temperature responsive means causes it to move out ofstarting position of the compressor and to remain out of that positionfor a predetermined time. The controller embodying the ambienttemperature responsive means may be disposed adjacent the compressor orcondenser, to be heated thereby or in fulfilling another object of theinvention the necessary heat may be obtained from an electric heater.

Another object is to provide a control device, preferably a switch, forrefrigerant compressors which is normally actuated by evaporatorpressure or temperature but which may be actuated by an ambienttemperature responsive thermostat, the latter embodying strain releasemeans so as not to interfere with operation of the switch by evaporatorpressure or temperature.

Another object is to provide a control device, preferably a switch,responsive to pressure and having bimetal means for compensating it forambient temperature.

Another object is to provide a compressor control arrangement comprisinga switch which may be. moved to ,on position in response to,

evaporator temperature or pressure provided a thermostat in therefrigerated space is calling for cooling, the thermostat having aheater which heats the thermostat when it is satisfied to cause it toperiodically cycle on and off so that opportunity is provided for theswitch to be closed by evaporator pressure or temperature at frequentintervals, the purpose of the arrangement being to provide for moreuniform cycling operation.

Figure 1 represents a refrigerating system controlled by a controllerembodying the ambient temperature responsive means of my inventiontherein,

Figure 2 represents a refrigerating system controlled by a differentform of controller embody ing my invention,

Figure 3 represents a compressor having the controller of my inventionmounted on the cylinder thereof,

Figure 4 represents a compressor and con-' denser with the controllermounted on the condenser,

Figure 5 represents a compressor with the controller mounted on thedischarge of the compressor,

Figure 6 represents a refrigerating system embodying a form of thecontroller of my invention having additional means responsive to thetemperature of the refrigerated space, and

Figure 7 represents a control switch having means for compensating theswitch for ambient temperature.

Referring to Figure 1 of the drawings, numeral It] represents thecompressor of a compression type refrigerating system. The compressor isdriven by an electric motor' ll by'means of a belt H. The dischargeside' of the compressor is connected to a condenser l3 by'means of apipe [4, and the condenser is connected to an expansion valve l5 bymeans of a'pipe Hi. The outlet of the expansion valve I5 is connected toan evaporator H by means of a pipe 18. The evaporator I! is disposed ina compartment to be refrigerated, the compartment being represented bythe broken lines l9. The outlet of the evaporator is connected to thesuction side of the compressor by a pipe 20.

The expansion valve i5 is a conventional type adapted to maintain apredetermined number of degrees of superheat of the refrigerant in theoutlet of the evaporator, the valve having a pressure chamber connectedby a capillary tube 2| to a thermostatic bulb 22 disposed in intimate Ierant of 15, for example.

heat exchange relation with the outlet of the evaporator.

The compressor motor II is controlled primarily by a controller 25 whichis essentially the same as the controller disclosed in detail in theapplication of Judson and Kronmiller, Serial No. 196,447, filed March1'7, 1938, now Patent No. 2,244,783, granted June 10, 1941. Thecontroller 25 operates jointly in response to head pressure and suctionpressure. The controller comprises a generally rectangular casing withinwhich is mounted an expansible and contractible bellows 26 which isconnected to the suction pipe 20 by a tube 2'! so as to expand andcontract in accordance with changes in suction pressure. At the movableend of the bellows 26 is a stem 28 which engages an intermediate portionof a lever 29, the lower end of which is crimped as shown and whichnormally engages a knife edge on a fixed member 30, the lever 29 beingoperable to pivot about the knife edge. The upper end of the lever 29 isattached to an adjusting screw 3| extending through a sidewall of thecasing of the controller 25 by means of a tension spring which normallyurges the lever 29 against the stem 28. The lever 29 carries aninsulating mernber 33 and mounted on this insulating member is a contactbracket 34 carrying an electrica-l contact 35 and another electricalcontact 36. The contact 35 cooperates with a contact 3'5 carried on aflexible bracket 38 mounted within the controller 25, the mounting meansforming an electrical terminal 39. Theupper end of bracket 38 engages acam 40 which acts as a stop, the cam having a gradually rising surfaceas shown and being mounted on a shaft 4| which extends to the exteriorof the casing of the controller 25 so that the cam can be adjusted fromoutside the controller. The contact 36 cooperates with a contact 45carried on a contact bracket 46 which is mounted within the casing ofthe controller, the mounting means forming an electrical terminal 4'!.The upper end of the bracket 45 engages a cam 48 similar to the cam 46and which is also mounted on a separate shaft rotatable from outside thecontroller 25 for adjusting the cam which acts as a stop for the bracketmember 46.

When the suction pressure rises, the bellows 26 expands moving the lever29 in a clockwise direction causing contact 35 to be brought intoengagement with contact 3'! and causing contact to engage contact 45later at a higher suction pressure which may be a pressure correspondingto a temperature of 33 F. of the refrigerant in the system. As willpresently be described, the compressor is not started in operation untilcontact 35 engages contact 45, and inasmuch as th s does not occur untilthe pressure of the refrigerant has risen to a value corresponding to atemperature of the refrigerant above freezing, the evaporator mustrefrost before the compressor can be started after the termination ofthe preceding cycle. When the compressor is started, the suctionpressure falls, causing the bellows 26 to contract permitting lever 29to move in a counter-clockwise direction. When this occurs contact 36first disengages from contact 45, and at a lower suction pressurecontact 35 disengages from contact 3! and this may occur, for example,at a relatively low evaporator pressure corresponding to a temperatureof the refrig- As will presently be pointed out, the compressor is notstopped until contacts 35 and 31 are disengaged. By adjusting the cams46 and 48, the positions of the brackets 38 and 46 can be adjusted, andconsequently the positions of contacts 31 and 45 can be adjusted withrespect to their associated contacts to thereby adjust the suctionpressures at which the contacts engage and disengage. Obviously byreason of the separate cams and contact brackets, the cut-in and cut-outpressures can be separately adjusted.

Numeral 5i} designates a second expansible and contractible bellowswithin the casing of controller 25, this bellows being connected to thedischarge pipe of the compressor by a tube 5!. At the movable end ofbellows 50 is a stem 52 which normally engages an intermediate point oflever 53, the upper end of which is crimped and which engages a knifeedge formed on a fixed member 54. The lever 53 is adapted to pivot aboutthe knife edge on member 54 and it is normally urged in a clockwisedirection into engagement with stem 52 by a coil spring 55 attached to ascrew 55 extending through a sidewall of the casing of controller 25 andadjustable from outside the casing for adjusting the tension of thespring. The lower end of lever 53 carries a pusher 57 arranged to engagethe lower end of contact bracket 46 when the bellows 50 expands, thecontact bracket 46 extending below the terminal 41. Adjacent the lowerend of bracket 45 is a contact 59 which is normally in engagement with acontact 66 on an electrical terminal post 53. Numeral 52 designates acontact bracket mounted within the casing of controller 25, the mountingmeans forming an electrical terminal 63. The bracket 52 carries acontact 54 which is normally in engagement with a contact 55 carried onan electrical terminal '56.

The pusher 5? has a shoulder 81 arranged to engage the lower end ofbracket 52 when the bellows 58 expands moving the pusher 5? to theright. The purpose of the bellows 50 and its associated contactingarrangement is to prevent the compressor from being started at too higha head pressure such as would be apt to overload the compressor motor aswill presently be described. When the head pressure rises, the bellows50 expands moving the lever 53 in a counterclockwise direction movingthe pusher 5'i to the right. When the head pressure rises to pounds, forexample, the end of pusher 57 engages the lower end of bracket 46causing contact 59 to disengage from contact 60. If the head pressurecontinues to rise, upon further movement of pusher 51 to the right, at asomewhat higher head pressure which may be pounds, for example, theshoulder 61 engages the lower end of bracket 62 causing contact 64 to bedisengaged from contact 65. As will presently be described, in order forthe compressor motor to be started, the head pressure must have fallento 140 pounds, but after it has been started it can be continued inoperation provided the head pressure does not rise above 180 pounds.

Included within the casing of controller 25 is a relay designated by thenumeral Hi. The relay "Hi comprises a winding H having an armatureassociated therewith which is attached to movable switch blades '12 andT3, the switch blades cooperating with fixed electrical contacts 74 and35 respectively. When the winding ll of the relay is energized thearmature is moved in a direction to move the switch blades intoengagement with their associated fixed contacts. Also mounted within thecasing of the controller 25 is an overload device designated by thenumeral 16 which may be of a conventional type. The overload devicecomprises a pair of contacts 11 and 19 which are disposed in the relaycircuit, as will presently be described, and which are actuatable by aheat responsive device responsive to heat generated by an electricheater 19 in the form of a resistance connected in the load circuit,that is, in the compressor motor circuit. The overload device it mayhave a manual lever 80 for resetting it to closed position after it isopened in response to an overload. Numerals 8| and 82 designate a pairof electrically connected terminals Within the casing of controller 25.

Under some circumstances the compressor of the system may be located ina relatively cold location, such that the suction pressure might not attimes rise to a high enough value to causev closure of contacts 39 and.45 to bring about starting of the compressor motor. To insure that thecompressor motor may be started under such circumstances, I haveprovided an additional temperature responsive device responsive to thetemperature in the vicinity of the compressor for starting thecompressor motor even though the suction pressure does not rise highenough to close contacts 39 and 45. The temperature responsive device ismounted within the casing of controller 25 and is designated generallyby the numeral 85. It comprises a housing 86 which may be made ofsuitable composition, the housing having a cover 81 which may be securedto the housing by means of a bolt 88. housing is a bimetal temperatureresponsive element 89 carried by bracket 96. At one end of element 89 isan electrical contact 9| cooperating with a fixed contact 92 within thehousing 89. Bearing against an intermediate point of the element 99 is ascrew 99 adjustable from outside of the housing 86 for adjusting thespacing of contacts 9| and 92 to adjust the temperature at which thecontacts will be brought into engagement. Upon a fall in temperature thelower portion of element 89 warps to the left and normally screw 93 isso adjusted that contacts 9| and 92 will be brought into engagement at atemperature of 40 F., for example. It will be understood that thecontroller 25 as a whole is mounted in the vicinity of the compressor sothat the element 89 is responsive to the ambient temperature around thecompressor. When the compressor has been started by the device 85, itmay be kept in operation by other parts of the control mechanism and itis not desired that the compressor operate for a short period and thenbe immediately restarted by the device 85. Thus, after the device 85 hasclosed its contacts for starting the compressor, it is desirable thatthe element 89 disengage contact 9| from contact 92 relatively soon andmaintain the contacts separated for a relatively long period of time,for example, an hour. Thus Ihave constructed and arranged device 85 soas to act as a timer to maintain the contacts open for perhaps an hourafter they have been closed to start the compressor. The device 85 aspreviously pointed out is mounted within the casing of the controller25. When the relay 19 is energized (energization of the relay causingoperation of the compressor, as will presently be pointed out), itswinding generates a certain amount of heat as does the heater 19 of theoverload device 19. The element 39 of the device 85 and the otherelements of the controller 25 have considerable thermal. mass, and afterit has closed the contacts 9| and 92, the heat generated within thecontroller 25 will cause the element 89 to warp Within the in adirection to separate the contacts, and due to the mass of thecontroller it will accumulate a considerable amount of the heatgenerated within the controller and this heat will maintain the device95 in open position of its contacts for a period of an hour, forexample, after the compressor has been stopped and there is no furthergeneration of heat within the controller 25, the timed period of coursedepending on the ambient temperature around the controller. After theone hour period, reclosure of contacts 9| and 92 will depend on theambient temperature falling below 40 F.

To provide the necessary heating for opening contacts 9! and 92 andmaintaining them open for a timed period, the controller 25 may bemounted in a position to be affected by heat generated by therefrigerating system. For instance, in Figure 3 there is shown acompressor with the controller 25 of Figure 1 mounted on the compressorcylinder to be heated thereby. Figure 4.- shows a compressor and acondenser with the controller 25 mounted on the condenser so as toderive heat from the condenser. Figure 5 shows a compressor with thecontroller 25 of Figure I mounted on the discharge of the compressor.

The bimetal element 89 is so constructed that after the compressor hasbeen started the heat generated either by the controller itself, or bythe compressor, or at the condenser will be sufficient to cause theelement to open its contacts after approximately one minute.

While such arrangements have not been shown, the controller may also bemounted directly on the motor, or if an air cooled condenser is used,the controller may be mounted in the stream of warm air passed over thecondenser.

It will be understood of course that when the compressor is started inoperation the ambient temperature surrounding it will rise, and thisrise in temperature will also tend to keep the device in open position.Of course after the compressor has stopped and after the expiration ofthe timing period, the ambient temperature will have fallen back tonormal, and as pointed out above reclosure of contacts 9| and 92 willdepend upon the ambient temperature falling below 40 F.

The controls for the compressor motor include a thermostat 99 in therefrigerated compartment l9. The thermostat 99 comprises an expansibleand contractible bellows I90 having a stem engaging a pivoted lever NH.The lever llll carries a mercury switch Hi2 having elec-- trodes at itsleft end. When the temperature in the refrigerated compartment rises toa predetermined value, which may be 42 F. for example, the bellows lllllexpands moving the lever |0| in a counterclockwise direction causingclosure of mercury switch I82. As will presently be explained, themercury switch I02 must be closed in order to start the compressormotor. When the temperature in the refrigerated compartment falls to 40F., bellows I99 contracts sufficiently to move lever ID! in a clockwisedirection into a position wherein mercury switch I92 is opened. In otherwords, the thermostat 99 has a differential of 2 F.

In normal operation, the compressor motor [I will be started when themercury switch I92 closes indicating a need for refrigeration in thecompartment l9, provided all of the contacts responsive to suction andhead pressure within the controller 25 are closed. In other words,-

the head pressure must be below 140 pounds to prevent overloading of thecompressor motor upon starting and the suction pressure must have risento a value high enough to have caused defrosting of the evaporator. Whenthe above conditions prevail a circuit is completed for the relay I asfollows: from wire I to terminal 66 through contacts 65 and 64, contactbracket 62, terminal 63, wire I06, mercury switch I02, wire I01,terminal 39, contact bracket 39, contacts 31 and 35, contact bracket 94,contacts 36 and 45, contact bracket 46, contacts 59 and 0?], terminalBI, wire E08, Wire I09, contacts 1! and I8, Wire IIO, winding II, wireIII, terminals 82 and BI to wire H2. The wires I05 and H2 may beconnected to any suitable source of power not shown; When the winding'5! of rela I0 is thus energized the switch blades I2 and I3 are movedinto engagement with their respective contacts. Engagement of blade 12with contact '34 completes a maintaining circuit for relay winding IIwhich by-passes suction pressure contacts 36 and 45 and head pressurecontacts 59 and 60 so that after the relay is energized it will be keptenergized through the maintaining circuit even though the suctionpressure falls below the value at which contacts 35 and 45 close andeven though the head pressure rises above 140 pounds. The maintainingcircuit is as follows; from wire I05 to terminal 66, contacts 65 and 09,contact bracket terminal 53, wire I06, mercury switch I02, wire I07,terminal 39, contact bracket 38, contacts 31 and 35, contact bracket 34,wire H3, wire H4, contact I4, switch blade I2, wire H5, wire I09,contacts TI and I8, wire H0, winding 1 I, wire I I I, terminals 82 and9! back to wire I I2.

Engagement of switch blade I3 with contact 15 completes a circuitenergizing the compressor motor as follows: from wire I05 to terminal65, wire IIG, to overload heater I9, wire II I, contact I5, switch bladeI3, wire II8, compressor motor I I, wire I I9, terminals 82 and M backto wire I I2. The relay I0 remains energized keeping the compressor inoperation until either the suction pressure falls to the value at whichcontacts 35 and 31 open so as to interrupt the above describedmaintaining circuit or until the said maintaining circuit is interruptedby opening of mercury switch I02 in the event of thermostat 99 becomingsatisfied. The maintaining circuit may also be interrupted in the eventthat head pressure rises above 180 pounds causing contacts 54 and 65 tobecome separated. Normally, however, the reriy 70 will be deenergized toterminate an operating cycle either in response to suction pressure orin response to the thermostat 39.

As pointed out above, under some circumstances when the compressor is ina relatively cold location wherein the suction pressure might not risehigh enough to cause contacts 36 and 45 to close for energizing therelay, it is necessary to rely on other means for causing the compressormotor to start. As pointed out above, the controller 25 is located inthe vicinity of the compressor so that the device 85 is responsive tothe ambient temperature surrounding the compressor, and this device isset to normally close its contacts at a temperature of 40 F., thistemperature being exemplary of one below which the air surrounding thecompressor would be so cold that the suction pressure would not risehigh enough to close contacts 36 and 05. When the device 85 closes itscontacts, a circuit is completed which energizes the relay I0, thiscircuit bypassing contacts 36 and 45 and being as follows:

from wire I05 to terminal 66, contacts 65 and 64, contact bracket 62,terminal 63, wire I06, mercury switch I02, wire I01, terminal 39,contact bracket 38, contacts 31 and 35, contact bracket 34, wire H3,wire I20, wire I2I, contacts 92 and 9|, element 89, wire I22, terminal41, contact bracket 06, contacts 59 and 60, terminal 6|, wire I08, wireI09, contacts 11 and I8, wire IIO, winding II, wire Ill, terminals 82and 8| back to wire IE2. Completion of this circuit energizes relay 10causing starting of the compressor motor, as described above, and alsocausing completion of the above described maintaining circuit throughthe thermostat 99, it being understood, of course, from the circuit justdescribed, that the thermostat 99 must be in a position demandingrefrigeration in order for the device 85 to start the compressor motor.

When the relay is energized and the compressor motor started the heatgenerated by the heater is and the relay winding are sufficient to causethe element 89 to separate the contacts 9| and 92 substantially oneminute after they have closed. Or if the controller 25 is mounted in oneof the positions previously described, the heat from the compressor orcondenser serves to cause the device 85 to open its contacts. After thedevice 85 opens its contacts, the compressor motor is kept in operation,however, through the maintaining circuit and it will continue to operateuntil the maintaining circuit is interrupted either by the suctionpressure opening contacts 35 and 31 or the temperature in therefrigerated compartment causing the thermostat 99 to become satisfied.While the compressor is in operation, the controller 25 accumulatesadditional heat tending to keep contacts 9| and 92 separated. As before,of course, the maintaining circuit may be opened by reason of the headpressure rising above pounds. Thus after the compressor motor has beenstarted by the device 85 it will operate for a length of time dependingboth upon what the suction pressure was at the time the compressor wasstarted and upon the temperature in the refrigerated space. If thesuction pressure has risen only slightly above the value at whichcontacts 35 and 31 closed at the time the compressor motor is started inresponse to the device 85, the compressor motor will be operated onlyfor a very short time, that is, until the suction pressure is reducedsufliciently to open the contacts 35 and 31.

After the compressor motor has been started by the device 05 and hasthen been stopped by one of the other control means, it is not desiredthat the compressor motor be started to recycle the system immediatelyor after a very short delay. Therefore the device 85 has the function ofa timing device so that its contacts will not become closed for a periodof substantially an hour after the compressor motor has been stopped.During the time that the compressor motor is operating, the controller25 will accumulate a certain amount of heat which is generated withinthe controller 25 or as has already been described this heat may beprovided by the compressor motor or condenser when the controller 25 ismounted in one of the positions shown in Figs. 3 to 5. The heat whichthe various parts of the controller will absorb is sufiicient to raiseits temperature a given amount, and after the compressor motor has beenstopped and the air in the vicinity of the compressor cools back tonormal substantially one hour of time will be required for thecontroller 25 to dissipate its accumulated heat and to permit element 89to again respond normally to the normal ambient temperature surroundingthe compressor. Thus, the arrangement provides for starting thecompressor motor even though the normal control responsive to suctionpressure will not do so. Short and frequent cycles are prevented byreason of the timing function which the device 85 has which provides forsubstantially an hour's delay after stopping of the compressor motorbefore it can again be started by the device 85.

Those skilled in the art will appreciate the advantages of my improvedarrangement inasmuch as it insures starting of the compressor motor whennecessary but will not start the compressor motor at other times. Thedevice utilized is very simple in construction and utilizes heat alreadyavailable in the system.

The invention may be carried out by closing contacts 9I and 92 by meansof a thermal bulb and bellows arrangement, the bulb being mounted on thecompressor discharge pipe or other place where it will be heated whenthe system is in operation.

Referring to Figure 2 of the drawings, I have shown a refrigerationsystem which is the same as the one disclosed in Figure 1, this systembeing provided with a different form of controller embodying thecompressor starting means of my invention, that is, the means responsiveto the ambient temperature around the compressor. In Figure 2 the systemitself is the same as in Figure 1 and the elements thereof are numberedthe same.

The controller of Figure 2 comprises a casing I25 having a horizontalshelf I26 therein and mounted on the shelf I26 is a snap switchgenerally designated by the numeral I21, the snap switch being enclosedwithin a Bakelite housing and being of the same type as disclosed indetail in the application of A. E Baak, Serial No. 307,991, filedDecember 7, 1939, now Patent No. 2,318,734, issued May 11, 1943. Theswitch I21 has on and off positions and is of the type adapted to remainin the position to which it is operated, the switch having a downwardlyextending operating stem designated by the numeral I25. Numeral I29designates an operating lever, the right end of which engages in a slotin the stem I28 and the left end of which is disposed between two camsI38 and HI which act as stops for the lever I29. The cam I39 has agenerallyrising contour and is mounted on a shaft extending through asidewall of the casing I25, the shaft being rotatable by knob !32outside of the casing for adjusting the position of the cam. The cam I3Isimilarly, has a generally rising contour and this cam also is mountedon a shaft which extends through a sidewall of the casing of thecontroller I25, this shaft being rotatable by knob I33 outside of thecontroller for adjusting the position of cam I3I.

Numeral I35 designates a, housing attached to the exterior of the casingof controller I25, there being an expansible and contractible bellowswithin the housing I35. The interior of the bellows is connected to thesuction pipe 20 of the compressor by a tube I36. The movable end of thebellows is connected to an operating. stem I31 which extends through afitting I38 into the interior of the casing of controller I25 and theend of the stem I31 carries a ball I39 disposed loosely in an opening atan intermediate point inthe lever I29. Numeral I40 designates a, leafspring attached to the upper side of lever I29 and engaging the ballI39. Numeral I4I designates a similar leaf spring attached to the lowerside of lever I29 and also engaging the ball I39, the stem I31 passingthrough the leaf spring MI. The leaf springs I48 and I4I by reason oftheir engagement with the ball I39 provide a strain release connectionbetween the stem I31 and the lever I29 to permit relative movementbetween the stem I31 and lever I29.

Numeral I42 designates a screw extending through the shelf I26 above thelever I29 and directly in line with the stem I31. The strain releasemechanism comprising the leaf spring 545 normally does not engage thescrew I42 in operation. The purpose of the screw will presently bedescribed.

In normal operation the switch I21 may be opened and closed in responseto changes in suction pressure. Thus, upon a rise in suction pressurethe bellows within housing I35 is expanded against the force of a springincluded in the bellows assembly causing the stem I31 to be movedupwardly until the left end of lever I29 engages the cam I38. Thisoccurs at a predetermined relatively high suction pressure which isnormally one high enough to insure that the evaporator has defrosted,and when this occurs the lever I29 pivots in a counter-clockwisedirection about the cam I38 as a fulcrum moving the stem I28 upwardly,which movement closes the switch I21. When the switch I21 closes, acircuit is completed to the compressor motor, as will presently bedescribed, for starting the compressor motor which causes the suctionpressure to fall. The point in the movement of stem I31 at which the endof lever I29 engages cam I39 and thus the pressure at which switch I21is closed may be adjusted by adjusting the cam I35. This of coursefollowing from the fact that the cam I30, as pointed out above, has agradually rising surface.

When the suction pressure falls, the bellows within housing I35collapses moving lever I29 downwardly until its left end engages camI3I. This occurs at a predetermined relatively low suction pressuredetermined by the adjustment of cam I3I, and when it does occur thelever I29 is moved in a clockwise direction moving the operating stemI28 downwardly and opening the switch I21. The point in the movement ofstem I31 at which the lever I29 engages cam I34 and consequently thepressure at which switch I21 is opened is adjustable by adjusting thecam I3I, the cam having a gradually rising surface as pointed out above.

The strain release connection between the stem I31 and the lever I29provides a release for the force exerted by the bellows if the bellowsshould continue to expand or contract after the end of the lever I29 hasengaged one of the cams and has thereby operated the switch I21.

As in the previous embodiment of the invention, the compressor may belocated in a locality wherein the temperature is so low that the suctionpressure may not rise high enough to cause closure of the switch I21 forstarting the com pressor. To insure that the switch I21 will be closedwhen there is a need for refrigeration even though the suction pressuredoes not rise high enough to close the switch, I have provided athermostatic device generally designed at I45. The device I45 comprisesa coiled bimetal element I44, the inner end of which is attached to arotatable pin I45 carrying an arm I51. The arm were I41 is normallyurged into engagement with a screw I48 carried by a bracket I45 by meansof a coil spring I50. The other end of the element I44 carries a fingerI5I adapted to engage the end of the operating stem I28. The element I44contracts upon rising temperature, and when the temperature in thevicinity of the compressor is high enough so that the switch I 21 can beclosed by suction pressure, for example, when the temperature is above50" F., the finger I5I normally does not engage the stern I 28. When thetemperature in the vicinity of the compressor falls so low however, thatsuction pressure does not rise high enough to close the switch I21, forinstance, when the temperatur surrounding the compressor falls into arange of from 35 F. to 50 F., for example, the element I44 will expand,moving finger I5I into engagement with the stem I28 and at apredetermined temperature moving the stem upwardly so as to close theswitch I 21 for starting the compressor. When the finger I5I is thusengaging the stem I28 the switch I21 may be opened in response tosuction pressure at substantially the same value as normally by reasonof the strain release arrangement formed by the arm I41 and spring I50.Thus, if finger I5I is engaging the stem I28, the stem I28 may be moveddownwardly by the lever I29 in response to a fall in suction pressure.When this occurs the stem I28 moves the finger I5I downwardly, and underthese circumstances bodily rotating the element I44 and arm I41 againstthe force of spring I50. The force exerted by spring I50 is relativelysmall and does not add appreciably to the downward force which the rightend of lever I29 must exert to move the stem I28 downwardly for openingswitch I21. The forces required to actuate switch I21 are relativelysmall, and of cours when the device I45 closes the switch I21 the forceexerted by finger I5I against the stem I28 is less than the forceexerted by spring I5I], the arm I41 under these circumstances remainingin engagement with the screw I48.

The device I45 may, if desired, be formed and arranged to act as a timeras in the previous embodiment. Thus the controller I25 may be mounted inany of the positions shown in Figures 3 to 5 so that when the compressoris as well, the controller has enough thermal mass so as to accumulate acertain amount of heat while the compressor is operating. This heatraises the temperature of the controller a given amount and after thecompressor has stopped and the air in the vicinity thereof cools to itsnormal value substantially an hour, for example, is required for it to'dissipate its accumulated heat and to again respond normally to ambienttemperature.

If it is not desired to mount the controller I25 in any of the positionsshown in Figures 3 to 5, an auxiliary heater I54 may be provided to heatthe element I 44 When th switch I21 is closed. The heater I 54 isconnected in series with the switch I 21 as will presently be describedso as to cause the device I45 to be heated during the time that thecompressor is in operation.

Numeral I55 designates a thermostat of the on and off type which islocated in the com- 12 partment to be refrigerated and which closes itscontacts at a predetermined value of temperature in the refrigeratedcompartment, these contacts being in series with the switch I21.

In normal operation the compressor motor is started when the thermostatI55 has its contacts closed indicating a need for refrigeration, andwhen the switch I21 is closed in response to suction pressure in themanner above described. When this occurs, a circuit for the compressormotor II is completed as follows: from wire I56 to thermostat I55, wireI51 to a terminal of switch I21, through switch I21 to its otherterminal, wire I59, heater I54, wire I50, motor II to wire IBI, thewires I56 and [GI being connected to any suitable source of power notshown. When the compress-or motor is started the suction pressure fallsand the motor operates until the above described circuit is interruptedeither by thermostat I55 or by opening of switch I21 in response tosuction pressure. During the time that the compressor motor is operatingthe heater I54 opens the element I44 maintaining the finger II out ofengagement with the stem I28.

Under some circumstances it may be desirable to operate the compressormotor solely from the thermostat I55 with the controller I25 acting onlyas a low pressure cut-out requiring manual reset. To provide for thistype of operation the switch I21 is manually closed and the screw I42 isscrewed downwardly far enough so that the lever I29 is prevented frombeing raised high enough to engage the cam I30 and cause closure ofswitch I21 in response to suction pressure. Under these circumstancesthe switch I21 normally remains closed and the compressor is started andstopped in response to the thermostat I55 alone, the thermostat I55normally becoming satisfied and stopping the compressor motor before theswitch I21 is opened in response to falling suction pressure. However,with this type of operation, if the suction pressure does fall to therelatively low value determined by the setting of the cam I3I, the leverI29 will be actuated to open the switch I21 and stop the compressormotor. If this occurs, the switch I21 will remain open until it ismanually reclosed, since screw I42 prevents upward movement of leverI29. It is to be seen therefore that with screw I42 adjusted asdescribed above for this type of operation, the controller I25 acts as alow pressure cut-out requiring manual reset.

When the ambient temperature surrounding the compressor falls into therange between F. and F., the suction pressure will not rise high enoughto cause closure of switch I21 for normal operation. Under thesecircumstances at a predetermined ambient temperature, the device I45will cause finger I5I to engage the stem I28 and close switch I21 asabove described. When the switch I21 is thus closed, if thermostat I iscalling for refrigeration at the time, the above described circuit forheater I54 and compressor motor II wlil be completed. When thecompressor is thus started, heat either from the compressor itself, orfrom the condenser if the controller I25 is mounted as shown in Figures3 to 5, or heat from the heater I54 if it is used, will cause theelement I44 to move the finger I5I away from the stem I28. As describedabove, after the compressor motor has stopped, substantially an hourwill be required for the controller I25 to dissipate its accumulatedheat after which element I will again respond nor mally to ambienttemperature.

From the foregoing, it is to be understood that the present embodimentof the invention provides for substantially the same type and sequenceof Operation as obtained in the previous embodiment, the presentembodiment. utilizing a different form of controller.

Referring to Figure 6 of the drawings, I have shown a modified form ofmy invention embodied in a system, the system being the same as thatshown in Figures 1 and 2 having its elements numbered the same.

The system of Figure 6 is controlled by a controller I65 which is likethe controller of Figure 2 in many respects but havin some additionalfeatures. Those elements of the controller I65 which are identical withcorresponding elements of the controller I25 of Figure 2 are numberedthe same. In Figure 6 the ambient temperature responsive devicecomprises a bimetal element I66, the inner end of which is rigidlysecured to the casing of the controller I65 and the other end of whichis adapted to engage operating stem I28 of the snap switch I21 and toclose the switch when the temperature within the casing of controllerI65 falls to a predetermined value within a range in this modificationof the invention of from 55 F. to 70 F. This temperature range withinthe casin of the controller corresponds to an ambient temperature rangearound the compressor of from 35 F. to 50 F. as will presently beexplained.

The controller I65 includes an electromagnetic device designatedgenerally at I61, this device being controlled by the thermostat 99 inthe refrigerated compartment, this thermostat being the same as that ofFigure 1 but having an electric heater I68 associated therewith, thepurpose of which will presently be described. In the controller I65 theswitch I21 is supported on a shelf I69 which has an angular bracketportion, as shown, which carries and supports an electrical windin I16forming part-of the electromagnetic device I61. Within the winding I16is a core I1I which cooperates with an armature I12 in the form of alever which is pivoted to the bracket portion of the shelf I69 and whichis normally biased in a clockwise direction by a coil spring I13 whichis attached to the left end of lever I12 and to the bracket portion ofshelf I69. is not energized thespring I13 urges the lever I12 in aclockwise direction causing the right end of the lever I 12 to engagethe lever I29 so as to urge the latter lever downwardly in a manner tomaintain the stem I28 in a downward position with the switch I21 open.With the parts of the controller I65 in the position shown in Figure 6,the suction pressure is normally inoperative to close the switch I21 byreason of the spring I13 and lever I12. However, with the parts in thisposition the suction pressure is effective to close the switch providedthe suction pressure rises to a higher than normal value sufiicient toovercome the force of spring I13, this higher than normal value ofcourse depending upon the spring I13.

The winding I16 is normally connected to a power source in series withthe electrical heating resistance I68. The circuit is as follows: froma. line conductor I14 to wire I15, winding I18, wire I16, wire I11,electrical resistance I68, wire I18, wire I 19 to line conductor I86,the line conductors I14 and I86 being connected to the power source.

When the Winding I16 14 The circuit for winding I16 'just described isnot sufficient to cause the armature of the electromagnetic device to beattracted; it remains in the position shown. The circuit of winding I16energizes it suiiiciently to cause it to generate a certain amount ofheat and this circuit through the electrical resistance I68 causes it togive off a certain amount of heat to heat the thermostat 99. Thethermostat 96 in the present modification may have a differential of 2F., for example; that is, it may close the mercury switch I62 at 42 F.and open it at 40 F. The resistance I68 may be such as to produce 3 ofheat, for example; that is,

it may raise the temperature in the refrigerated compartment locallyaround the thermostat 3 such that when the temperature within therefrigerated compartment is at 39 F. of above this value, with themercury switch I62 open, the heat from resistance I68 will heat thethermostat sufficiently to cause it to close the mercury switch I62.When the mercury switch I62 closes, an additional circuit is completedfor winding I16 which shunts the heater I68, this circuit being asfollows: from line conductor I14, through wire I15, winding I16, wireI16, wire I8I, mercury switch I62, wire I82, wire I19 back to lineconductor I86. The latter circuit places winding I18 directly across theline. The latter circuit carries suflicient current so as to energizethe electromagnetic device I 61 sufliciently to cause its armature to beattracted, that is, the lever I12 is rotated in a counter-clockwisedirection against the force of spring I13 and is held in its rotatedposition. With the parts so positioned, the lever I29 is not restrainedfrom normal operation in response to suction pressure and the switch I21may under these circumstances be closed in response to suetion pressureat the normal cut-in pressure. When lever I12 has been moved away fromlever I29, as soon as the suction pressure rises to the cut-in value,the switch I21 will be closed for starting the compressor and as in theprevious embodiments the cut-in pressure is preferably high enough toinsure that the evaporator has defrosted in the meantime. The circuitfor the compressor is as follows: from line conductor I14 through wireI85, compressor motor I I, wire I85, switch I21 through wire I81 back toline conductor I86. When the compressor is started, the suction pressureis of course reduced and the operating cycle proceeds normally.

Operation of the system of course tends to reduce the temperature in therefrigerated compartment I9 and with the heater I68 not now energizedthe thermostat 99 will respond to the actual temperature in therefrigerated compar ment, and whenever this temperature is reduced below46 F., the thermostat 99 will open its switch 162 deenergizing the lastdescribed circuit for winding I16 and causing the original circuitthrough I68 to be reenergized. Interruption of the circuit throughmercury switch I92 will cause the electromagnetic device I61 to assumethe po sition shown in Figure 6, the lever I12 acting on lever I29 toopen the switch I21 terminating the operating cycle. It is seen,therefore, that the operating cycle does not begin until the thermostat99 is in a position calling for refrigeration and until the suctionpressure rises to the cut-in value. After the compressor has beenstarted the switch i2? will be opened to stop it whenever the thermostat99 becomes satisfied or when the suction pressure falls to the cut-outvalue causing the stem I28 to be moved downwardly to open the 1:) switchI21; The switch can of course be opened by suction pressure irrespectiveof the device I61.

When the thermostat 99 becomes satisfied as above described, the heaterI68 becomes reenergized so as to heat the thermostat to cause it toagain assume unsatisfied position. In this manner it is to be seen thatnormally the thermostat 99 will cycle on and off by reason of heater I68so as to cause the device It? to intermittently permit closing of switchI2! in response to suction pressure. In the present form of theinvention the thermostat 99 normally cycles on and off approximatelyevery ten minutes. That is approximately ten minutes of operation of thecompressor are required for switch I62 to open and the heater closes itin a half minute, for example. By reason of the cycling operation ofthermostat 99, opportunities are provided at frequent intervals for theswitch I21 to be closed in response to suction pressure, and after thecompressor has been thus started its operation is not prolonged but itis terminated whenever the thermostat 99 becomes satisfied. Thus, theoperation provides for relatively short and frequent cycles of thecompressor which operation is desirable particularly under light loadconditions to prevent the humidity within the refrigerated compartmentfrom rising too high such as would occur if there were long off periodsof the compressor. The more frequent compressor operations resultingfrom the use of the heater type thermostat prevents the occurrence ofsuch long off periods of the compressor and thus the humidity is keptwithin a desired range.

The current flow through the winding I'Iii through the above describedcircuits causes the winding to generate a certain amount of heat whichnormally will maintain the temperature within the controller I65 atapproximately above the ambient temperature. It is for this reason thatthe element I55 is arranged to close the switch I21 at a temperaturesetting approximately 20 higher than the setting would be if the elementI66 responded directly to the ambient temperature. When the ambienttemperature is above the range of from F. to R, such that there is noneed for closing the switch I2! by means of the element I66, the heatgenerated within the controller I keeps the free end of the element IE5disengaged from the stem I28. The element E65 expands in response tofalling temperature and when the ambient temperature falls into therange just mentioned, that is, the range between 35 F. and 50 F. thefree end of the element I66 will engage the operating stem $28 at apredetermined temperature within the casing of controller I65 and willclose the switch I21 for starting the compressor. This operation issubstantially the same as that, described in connection with theprevious embodiment. The temperature at which the switch I2! is closedby the element I56 will be substan-- tially 20 higher than the ambienttemperature as explained above. By reason of the frequent cycling of thethermostat 99 and the electromagnetic device I67, the temperature withinthe casing of controller I65 is normally maintained at substantially 20above the ambient temperature as described, that is, winding I19 ispractically continuously energized. Without the heater in combinationwith the thermostat 99 the device I51 would not be so frequentlyenergized and the temperature within the casing of the controller I65would not be as constant. Under such circumstances upon energization ofthe device It! the temperature within the casing of controller I65 wouldrise to a value above normal and this rise in temperature would preventthe device I66 from closing the switch I27. Thus the heater typethermostat 99 cooperates with the control device I65 to enable theambient thermostat I69 to start the compressor at the proper value ofambient temperature and to be otherwise disengaged from the operatingstem I28 of the switch I2I.

From the foregoing it will be apparent to those skilled in the art thatin the present embodiment of the invention I have provided anarrangement wherein the compressor is started in response to suctionpressure and in response to the thermostat in the refrigeratedcompartment and is stopped either when the temperature in therefrigerated compartment is reduced to a predetermined value Or when thesuction pressure falls to a predetermined value. As pointed out above,the arrangement provides for desirable cycling operation withoutprolonged operating periods which are particularly desirable when theload is not especially heavy.

Referring to Figure '7 of the drawings, I have shown another modifiedform of my invention comprising a controller which is essentially thesame as that of Figure 2 but having means for compensating the cut-inand cut-out points of the switch in response to ambient temperature. Theelements of the controller of Figure '7 are essentially identical withthose of the controller of Figure 2 and they are numbered the same. Thecontroller of Figure '7 however additionally includes a bowed bimetalelement I99 responsive to ambient temperature. The lower end of theelement I is attached to the inside of the casing of the controller andthe other end has a curved portion, as shown, abutting the leaf springI4I, this portion being forked, with the stem I3! engaged between theprongs of the fork. The upper end of the element I90 tends to urge thelever I29 upwardly with a force depending upon the temperature affectingthe element 599, the element I90 thus assisting upward movement of thestem I31 and causing the switch I21 to be closed at a lower value ofsuction pressure than if the controller were not compensated for ambienttemperature. When the suction pressure is falling and the lever I29 isbeing moved downwardly by the stem I31 the element I90 resists suchdownward movement depending upon the temperature affecting the elementI99 and thus makes it necessary for the suction pressure to fall to alower than normal value in order for the switch I47 to be opened. Theelement I90 expands upon falling temperature and contracts upon risingtemperature; that is, it warps in a direction to urge the lever I29upwardly with greater force when the ambient temperature falls. Theelement I9!) is so arranged that when the ambient temperature is above50 it exerts negligible force upon the lever I29 so as not to affect thecut-in and cut-out points of the controller. When the ambienttemperature falls into a range of from 35 F. to 50 F., such that thesuction pressure may not normally rise high enough to cause closure ofthe switch :21, the element I90 efiectively compensates the cutin andcut-out points of the switch I21 as above described, the elementlowering both the cut-in and cut-out points of the switch.

The embodiments of my invention which I have disclosed and described indetail are representative of its preferred forms. There are various 17modifications and variations which may be made in the invention butwhich fall within its spirit and scope. My disclosure is therefore to beinterpreted in an illustrative rather than a lim-.

iting sense and the invention is to be limited only in accordance withthe claims appended hereto.

I claim as my invention:

1. In refrigerating control apparatus of the character described, incombination, a control device comprising a switch having switchoperating means, pressure operable means for actuating the switchoperating means, and ambient atmosphere temperature responsive meansindependent of said pressure operable means arranged to engage theswitch operating means below a predetermined relatively low temperaturefor operating the switch to a circuit making position, said temperatureresponsive means being so constructed and arranged as to be normallydisengaged from said switch operating means so as not to interfere withthe operation of the switch.

2. In cooling control apparatus of the character described, incombination, a control device comprising a switch having switchoperating means, pressure operable means for actuating the switchoperating means, ambient temperature responsive means arranged to engagethe switch operating means below a predetermined relatively lowtemperature for operating the switch, said temperature responsive meansbeing so constructed and arranged as to be normally disengaged from saidswitch operating means so as not to interfere with the operation of theswitch, and means adapted to heat said temperature responsive means whenthe switch is operated to cause said latter means to be retracted.

3. In apparatus of the character described, in combination, a controldevice comprising a, switch having switch operating means, pressureoperable means for actuating the switch operating means, ambienttemperature responsive means arranged to engage the switch operatingmeans at a predetermined temperature for operating the switch, saidtemperature responsive means being so constructed and arranged as to benormally disengaged from said switch operating means so as not tointerfere with the operation of the switch, and electrical impedancemeans adapted to heat said temperature responsive means when the switchis operated to cause said latter means to be retracted, said temperatureresponsive means being adapted to absorb a substantial amount of heatand to dissipate said heat relatively slowly whereby the temperatureresponsive means remains in a retracted position for a predeterminedtime after having been heated.

4. In cooling control apparatus of the character described, incombination, a control device comprising a switch having switchoperating means, pressure operable means for actuating the switchoperating means, ambient temperature responsive means arranged to engagethe switch operating means below a predetermined temperature foroperating the switch, said temperature responsive means being soconstructed and arranged as to be normally disengaged from said switchoperating means so as not to interfere with the operation of the switch,electrical impedance means adapted to be placed in and out of operationby said switch and adapted to generate heat when energized so as tocause said temperature responsive means to be retracted when said switchcauses operation of the means controlled thereby.

5. In cooling control apparatus of the charac- 18 ter described, incombination, means comprising a switch, operating means normally movablein one direction for closing the switch and movable in another directionfor opening the switch, automatic means for actuating the operatingmeans,

temperature responsive means coasting with said operating means in amanner to hold said switch in a closed position when the temperatureofthe apparatus is below a predetermined value, and manually adjustablemeans adjustable to a position preventing automatic movement of theswitch operating means to said closed position of the switch whereby theautomatic means can operate the switch only to the other position.

6. In a control device for a refrigerating compressor, in combination,control apparatus, a housing for said control apparatus, said housingand apparatus being in heat transfer relationship and having heatcapacity, said apparatus including switch means for controlling acircuit, pressure responsive means for normally operating said switchmeans, temperature responsive means effective, when the temperature ofsaid control device is below a predetermined value, to cooperate withsaid pressure responsive means for controlling said circuit in a circuitenergizing manner, and electrical impedance means within said housingfor emitting heat when energized to thereby increase the temperature ofsaid device.

'7. In a control device, in combination, control apparatus, a housingfor said apparatus, said housing and apparatus being in heat transferrelationship and having heat capacity, said apparatus including switchmeans for controlling a circuit, pressure responsive means for actuatingsaid switch means, and means responsive to the temperature of saiddevice for actively supplementing the circuit controlling operation ofsaid switch means when the temperature of said device is below apredetermined vaiue.

8. In a control device, in combination, control apparatus includingswitch means, pressure responsive means for operating said switch meansto one circuit controlling position at a predetermined relatively highpressure and to another circuit controlling position at a relatively lowpressure, means responsive to the temperature of said device forsupplementing said pressure responsive means in controlling said switchmeans when said temperature is below a predetermined value, electricalimpedance means effective for heating said device when energized andarranged to be controlled by said switch means, and housing means forsaid apparatus, said apparatus and housing means being in heat exchangerelationship and having sufficient heat capacity such that said device,when heated, requires an appreciable period of time for cooling belowsaid predetermined value.

9. The apparatus of claim 8 in which the switch means comprises aplurality of switches, one of which is independently operable by saidtemperature responsiv means, a circuit controlled by said one switchshunting the other switches of said switch means.

10. In a control device, in combination, switch means operable betweenopen and closed positions, pressure responsive means for operating saidswitch means between said positions, adjustable stop means fcrdetermining the pressure at which said switch means is operated,temperature responsive means effective in a manner to cause operation ofsaid switch means when the temperature of said device is below apredetermined value, and strain release means limiting 19 the force thatmay be exerted by said temperature responsive means.

11. In a control device, in combination, switch means, pressureresponsive means for operating said switch means between circuit openand closed positions, means for determining the pressures required fornormally operating said switch means, force exerting temperatureresponsive means for causing operation of said switch means at lowerthan normal pressures when the temperature of said device is below apredetermined value, strain release means limiting the force that can beexerted by said temperature responsive means, and heater means arrangedto be energized when said switch means is closed and effective whenenergized to raise said device temperature.

12. In a control device, in combination, switch means, pressureresponsive means for normally operating said switch means, forceexerting temperature responsive means for diminishing the value ofpressure required to operate said switch means when the temperature ofsaid device is below a predetermined Value, and heat emitting forceexerting means variably opposing the force exerted by said temperatureresponsive means, the heat emitted by said heat emitting means, whenenergized, tending to raise the temperature of said device to thusrender said temperature responsive means ineffective.

13. In a control device including a housing, in combination, switchmeans, pressure responsive means for normally operating said switchmeans, ambient temperature responsive means for sup- 20 plementing theaction of said pressure responsive means on said switch means when thetemperature of the device isbelow a predetermined value, saidtemperature responsive means being ineiiective when the devicetemperature is above said value, spring urged lever means opposing theaction of said temperature responsive means, and electromagnetic meansfor controlling said spring urged lever, said electromagnetic meansemitting heat when energized, said heat increasing the temperature ofsaid device and thus influencing the action of said temperatureresponsive means, said housing being in heat transfer relation with atleast said electromagnetic means and said temperature responsive means,said device having an appreciable heat storag capacity.

ALWIN B. NEWTON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,951,446 Scheibell Mar. 20, 19341,974,991 Hutt Sept. 25, 1934 2,090,526 Eaton Aug. 17, 1937 2,121,079Eskin June 21, 1938 2,167,227 Wilson July 25, 1939 2,176,338 HarringtonOct. 17, 1939 2,184,339 Ettinger Dec. 26, 1939 2,273,540 Smith Feb. 17,1942 2,298,323 Wheeler Oct. 13, 1942 2,367,306 Newton Jan. 16, 1945

